1. Field of the Invention
This invention relates to a fiber-reinforced polyethylene terephthalate resin composition having excellent mechanical characteristics, high heat resistance, and high chemical resistance, which is widely used for various heating device such as electronic ranges, electromagnetic cookers and irons electric parts such as connectors and coil bobbins, and automobile parts such as reflectors.
2. Description of the Related Art
The characteristics of a crystalline polymer such as a polyethylene terephthalate resin depend greatly on the degree of crystallization. Accordingly, if a high heat resistance is desired, a crystal nucleating agent such as a metal salt of an organic carboxylic acid or an inorganic compound must be added and molding must be carried out under a mold temperature having a high level of 130.degree. to 140.degree. C.
Alternately, a method can be adopted in which a molded article obtained at a low mold temperature not exceeding 100.degree. C. is subjected to a post heat treatment or a similar post treatment for promoting and advancing the crystallization, whereby the heat resistance is increased.
However, in view of the operation stability and from the economical viewpoint, use of a high-temperature mold or post treatment is not preferred. If molding is carried out by using a low-temperature mold maintained at a temperature lower than 100.degree. C., the crystallization of the resin is not sufficiently advanced, and thus the release property is degraded. To enhance the release property, cooling must be slow, and therefore, a long time is required for cooling.
As a means of overcoming this disadvantage while carrying out the molding at a low mold temperature, a method is known of using a crystallization-promoting agent, and various crystallization-promoting agents are known.
For example, Japanese Examined Patent Publication No. 45-26225 proposes a method in which an ionic copolymer comprising an .alpha.-olefin and a salt of an .alpha.,.beta.-unsaturated carboxylic acid is added to polyethylene terephthalate. Furthermore, Japanese Examined Patent Publication No. 47-3027 proposes a method in which a polyalkylene glycol is used in combination with an inorganic filler such as talc. Moreover, a combined use of an ionic copolymer, a polyalkylene glycol type compound, and an inorganic filler is known from Japanese Unexamined Patent Publication No. 5922985.
Still further, a method is known in which polyethylene terephthalate is copolymerized with soft segments and a crystallization-promoting agent is incorporated, whereby the crystallization speed is improved. For example, Japanese Unexamined Patent Publication No. 56-55451 proposes a method in which an ionomer is added to a copolymer of polyethylene terephthalate with a polyalkylene glycol, and Japanese Unexamined Patent Publication No. 60-223856 proposes a method in which an ionomer and a polyalkylene glycol are added to a copolymer of polyethylene terephthalate with a polyalkylene glycol.
When these known polyethylene terephthalate resin compositions are injection-molded in a mold maintained at a relatively low temperature, for example, at about 80.degree. C., by using a hot water circulation type temperature-adjusting apparatus, which is advantageous from the economical viewpoint, the release property and mechanical strength are good, but the resulting molded articles do not have a completely satisfactory appearance.